atm: solos-pci: Fix potential deadlock on &cli_queue_lock

As &card->cli_queue_lock is acquired under softirq context along the
following call chain from solos_bh(), other acquisition of the same
lock inside process context should disable at least bh to avoid double
lock.

<deadlock #1>
console_show()
--> spin_lock(&card->cli_queue_lock)
<interrupt>
   --> solos_bh()
   --> spin_lock(&card->cli_queue_lock)

This flaw was found by an experimental static analysis tool I am
developing for irq-related deadlock.

To prevent the potential deadlock, the patch uses spin_lock_bh()
on the card->cli_queue_lock under process context code consistently
to prevent the possible deadlock scenario.

Fixes: 9c54004ea717 ("atm: Driver for Solos PCI ADSL2+ card.")
Signed-off-by: Chengfeng Ye <dg573847474@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/atm/solos-pci.c b/drivers/atm/solos-pci.c
index 94fbc3abe60e6a714c546bc2e8c6dce321742bbe..95f768b28a5e69d899246679eb5bef80f0bfe39f 100644 (file)
--- a/drivers/atm/solos-pci.c
+++ b/drivers/atm/solos-pci.c
@@ -449,9 +449,9 @@ static ssize_t console_show(struct device *dev, struct device_attribute *attr,
        struct sk_buff *skb;
        unsigned int len;
 
-       spin_lock(&card->cli_queue_lock);
+       spin_lock_bh(&card->cli_queue_lock);
        skb = skb_dequeue(&card->cli_queue[SOLOS_CHAN(atmdev)]);
-       spin_unlock(&card->cli_queue_lock);
+       spin_unlock_bh(&card->cli_queue_lock);
        if(skb == NULL)
                return sprintf(buf, "No data.\n");